Suppression Of Marestail In Various Cover Crop and Herbicide Systems Within Soybean Production.

With an increasing number of herbicide resistant weed species, it has become apparent that alternative methods of weed suppression should be examined. The objective of these studies was to determine the amount of weed suppression that can be achieved using various cover crop and herbicide systems. Fall cover crops, including wheat (Triticum aestivum), rye (Secale cereale), barley (Hordeum vulgare) and annual rye grass (Lolium multiflorum), were seeded in November 2012 while spring oats (Avena sativa) were seeded in April 2013 at Manhattan, KS. These cover crops followed two different crops: sorghum (Sorghum bicolor) and soybean (Glycine max). These studies also included fallow plots that received herbicide treatments: fall applied Dicamba, fall applied Valor XLT plus Dicamba, spring applied Dicamba and spring applied Valor XLT plus Dicamba.   Valor XLT and Dicamba were also spring applied to plots of rye. Weed populations and biomass accumulation were quantified for the different cover cropping systems. Cover crops differed in their ability to suppress weeds after both crops. In both stubble situations, rye that received a spring herbicide treatment with residual action (Valor XLT plus Dicamba) had the greatest reduction of weed biomass compared to the control (99% reduction in sorghum and 92% in soybean) and highest percentage (100% control) of marestail suppression among both systems compared to a control. Herbicide treatments provided the second highest level of suppression in both sorghum and soybeans, with 97% and 96% control, respectively. Cover crops suppressed marestail 37% in sorghum and 10% in soybeans compared to the control. Data indicates that combining both cover crop and herbicide systems may provide growers with a viable alternative weed suppression mechanism.